Two-dimensional Temperature Distribution of Strip in Preheating Furnace of Continuous Annealing Line

Two-dimensional temperature distributions of the steel strip are studied by the energy balance method with the aid of finite-element analysis. The space of the preheating furnace is divided into several enclosures in which the mechanisms of heat convection, heat radiation, and contact heat transfer are taken into account. The longitudinal and transverse temperature distributions of the strip are finally iteratively calculated by using the method of energy balance. The strip exhibits a significant temperature rise after contact with the rolls and shows a nonuniform temperature distribution along the width direction with smaller magnitude at two sides.     

Longitudinal residual warpage of strip in continuous annealing line

After the heat treatment in continuous annealing line (CAL), the strip always exhibits phenomenon of residual warpage during punching process. This geometric defect is mainly attributed to the residual stress induced in the line and has a close relation with the temperature history of the strip. It becomes more serious for the wider strip and may significantly degrade the quality of the products. The contents of this study are mainly composed of establishing the energy model of the strip and roll to estimate the temperature distributions of the strip and the surface temperature of the roll, estimating the emissivity and equivalent heat transfer coefficient of the strip in each section of CAL, and establishing mechanical model of the strip to evaluate the distributions of contact pressure and residual stress of the strip especially along the width direction. Finally, the longitudinal residual warpage was calculated accordingly by virtual layers method (VLM). It was found that the residual warpage at both sides is larger than the central region. Moreover, the numerical results of strip warpage are well consistent with the experimental data which demonstrates the accuracy and reliability of the proposed method.     

Temperature Distribution of Taper Rolls in Preheating Furnace of Cold Rolling Continuous Annealing Line

In this article, three-dimensional (3-D) transient temperature distributions of taper rolls in a continuous annealing line (CAL) are investigated using finite-element analysis. Since the temperature of the strip is closely related to the surface temperature of the rolls due to the effect of contact heat transfer between them, it is crucial to determine the accurate surface temperature distributions of rolls in CAL. It is found that the temperature history of a roll remains identical and exhibits a radial-dependent distribution as the Peclet number of the roll decreases to a suitable small value, corresponding to a low angular speed of the roll. The computational time for the case with low Peclet number, however, can be significantly reduced. Moreover, it is seen that the results of a two-dimensional (2-D) model are in good agreement with those of the 3-D model in the central region covered with the strip, while the computational time of the former is about one-twentieth of the latter. Consequently, a minimum computational cost can be achieved by using 2-D model with a suitable lower value of Peclet number without sacrificing the accuracy of the simulation results.     

镀锌退火炉改为镀锌-连退两用退火炉的研究与应用

对比了冷轧带钢镀锌和连退两种工艺热处理曲线的同异,介绍了退火炉改造的内容,通过改造,机组能够适应镀锌、连退两种工艺生产,为企业带来很好的经济效益。     

Transient Thermoelastic Analysis for a Laminated Composite Strip with an Interlayer of Functionally Graded Material

This paper is concerned with the theoretical treatment of transient thermal stress problem involving a laminated composite thick strip with an interlayer of functionally graded material due to nonuniform heat supply in the width direction. The thermal and thermoelastic constants of the interlayer of functionally graded material are assumed to vary exponentially in the thickness direction. We obtain the exact solution for the two-dimensional temperature change in a transient state, and thermal stresses of a simple supported strip under the state of plane strain. Some numerical results for the temperature change, the displacement and the stress distributions are shown in figures. Furthermore, the influence of the thickness and position of the interlayer is investigated.     

THERMOELASTIC PURE BENDING OF NONHOMOGENEOUS PRISMATIC BARS

By using a Bernoulli-Euler type beam theory, a simple solution is obtained for the general problem of the thermoelastic pure bending of nonhomogeneous prismatic bars. Within this framework, the elastic modulus and temperature distributions can vary arbitrarily over the bar cross-section, and the elastic modulus and thermal expansion coefficients can be temperature dependent. The analysis is valid for time-dependent temperature variations and can therefore be used for analyzing warping and residual stresses induced by transient temperature fields. An analysis of a bi-material channel-sectioned beam is used to show that the addition of ribs significantly reduces the thermoelastically induced warping in bimaterial strips caused by temperature excursions. It is shown that thermoelastic warping in a three-layer tri-material strip cannot be reduced by using a middle layer with an elastic modulus much lower than the modulus of the surrounding layers.     

Influence of thermal sensitivity of the materials on temperature and thermal stresses of the brake disc with thermal barrier coating

The time-dependent frictional heating of a disc with applied thermal barrier coating (TBC) on its working surface was investigated. To determine the temperature fields in the coating and the disc a one-dimensional friction heat problem during braking was formulated, with taking into account the dependence of thermal properties of materials from temperature. A model was adopted for materials with a simple non-linearity, i.e. materials whose thermal conductivity and specific heat are temperature dependent, and their ratio – thermal diffusivity is constant. The linearization of the corresponding boundary-value heat conduction problem was made by the Kirchhoff transformation and the linearizing multipliers method. A numerical-analytical solution to the obtained problem was found by Laplace transform method. Knowing the temperature distributions, quasi-static thermal stresses in the strip (TBC) with taking into account change in temperature mechanical properties, were determined. The distribution of temperature and thermal stresses in the strip made from ZrO₂ deposited on the UNS G51400 steel disc, was investigated.     

环形加热炉热工过程CFD数值模拟及其应用

借助CFD商业软件CFX，考虑流动、辐射、燃烧等，对宝钢环形加热炉的热工过程进行了数值模拟，得到了炉膛内的温度、速度矢量等热工参数的分布图。通过简化处理，对环形加热炉各控制段内的加热过程进行了模拟分析，并根据所得到的管坯表面辐射热流、热电偶温度及管坯表面温度研究了各个段总括热吸收率的分布情况，主要分析了总括热吸收率在管坯圆周方向、长度方向以及各个段之间的变化规律。     

Model for prediction of strip temperature in hot strip steel mill

Proper functioning of set-up models in a hot strip steel mill requires reliable prediction of strip temperature. Temperature prediction is particularly important for accurate calculation of rolling force because of strong dependence of yield stress and strip microstructure on temperature. A comprehensive model was developed to replace an obsolete model in the Western Port hot strip mill of BlueScope Steel. The new model predicts the strip temperature evolution from the roughing mill exit to the finishing mill exit. It takes into account the radiative and convective heat losses, forced flow boiling and film boiling of water at strip surface, deformation heat in the roll gap, frictional sliding heat, heat of scale formation and the heat transfer between strip and work rolls through an oxide layer. The significance of phase transformation was also investigated. Model was tested with plant measurements and benchmarked against other models in the literature, and its performance was very good.     

实测罩式炉料温优化退火曲线

针对天津丽兴制品有限公司使用国产罩式炉进行冷轧带钢的生产情况,对60吨炉型进行了带钢温度的测试,根据测试数据结果分析,进行了退火曲线的优化。     

2008t/h四角燃烧煤粉锅炉烟温偏差实炉测试分析

大型四角切圆燃烧锅炉的烟、汽温度偏差对其安全运行具有重要影响。在2008t/h锅炉上,对不同负荷工况下炉膛上部屏区烟温及屏式过热器壁温进行了测试。结果表明,汽温左高右低,大致成W型分布形态,而烟温呈M型分布,与汽温分布状态峰谷反向对应。认为炉膛上部空间残余旋转形成沿屏区宽度烟气流量的不均匀分布,因而烟气对受热面的冲刷强度不同,导致屏间烟气换热量存有差异,这是烟、汽温偏差产生的根本原因。     

3D thermo-electro-chemo-mechanical coupled modeling of solid oxide fuel cell with double-sided cathodes

A solid oxide fuel cell based on double-sided cathodes is developed in our group, showing special properties and many advantages under some harsh conditions. To optimize the cell further, a thermo-electro-chemo-mechanical coupled 3D model is developed to simulate the distributions of temperature, current density, fuel gas and thermal stress under different voltages. The numerical results indicate that the temperature distribution, current, fuel gases and thermal stress is non-uniform in the cell at different voltages. The distribution of thermal stress in the electrolyte is also non-uniform because of the un-even electrochemical reaction and convective heat transfer. Furthermore, the result shows that about 47%~54% of maximum 1st principal stress in SOFC is caused by the mismatch of coefficients of thermal expansion (CTEs) among materials, while the other part of the maximum 1st principal stress is mainly caused by temperature gradient.     

Mathematical Model and Its Application of Radial Effective Thermal Conductivity for Coil Heat Transfer in HPH Furnace

Temperature uniformity of steel coils in High Performance Hydrogen bell-type annealing furnace has a significant effect on their quality and production. The hot rolled coil can be considered as a periodically laminated material composed of steel layers and interface layers in radial direction. A new formula for the radial effective thermal conductivity has been proposed, which is based on surface characteristic, strip thickness and compressive stress of the rolled coil. Furthermore, it has been used to develop a heat transfer mathematical model for steel coils in the HPH furnace. The calculated annealing curves using this mathematical model are in good agreement with the experimental data.     

An analytical model for the prediction of strip temperatures in hot strip rolling

In hot strip rolling, sound prediction of the temperature of the strip is vital for achieving the desired finishing mill draft temperature (FDT). In this paper, a precision on-line model for the prediction of temperature distributions along the thickness of the strip in the finishing mill is presented. The model consists of an analytic model for the prediction of temperature distributions in the inter-stand zone, and a semi-analytic model for the prediction of temperature distributions in the bite zone in which thermal boundary conditions as well as heat generation due to deformation are predicted by finite element-based, approximate models. The prediction accuracy of the proposed model is examined through comparison with predictions from a finite element process model.     

耐火陶瓷纤维在连续退火生产线退火炉高温段上的应用

较为系统地介绍了攀钢冷轧厂连续退火生产线退火炉改造前后的设备组成,分析了改造前退火炉高温段砌筑材料的不足,制定了采用陶瓷纤维进行炉衬改造的技术方案,通过耐火陶瓷纤维应用前后炉衬材料性能与使用效果的对比分析,取得了退火吨钢能耗下降标煤10．14kg、炉顶及炉墙的外表温度明显降低以及明显改善带钢表面质量的优良效果,对同类型机组的设备改造提供了可靠的参考依据。     

Buckling of functionally graded plates under thermal,axial, and shear in-plane loading using complex finite strip formulation

A complex finite strip method was used to study the buckling of functionally graded plates (FGPs) under thermal and mechanical (longitudinal, transverse, and shear in-plane) loading. The mechanical characteristics of FGPs were assumed to vary through the thickness, according to power law distribution. The nonlinear temperature distribution in the direction of the plate thickness was assumed according to thermal conduction steady state conditions. In complex finite strip method, the polynomial Hermitian functions were assumed in the transverse direction and the complex exponential functions were used in the longitudinal direction to evaluate the standard and geometric stiffness matrices that have the ability of calculating the critical shear stress in contrast to trigonometric shape functions. The solution was obtained by the minimization of the total potential energy and solving the corresponding eigenvalue problem. In addition, numerical results for FGPs with different boundary conditions were presented and compared with those available in the literature and the interaction curves of mechanical and thermal buckling capacity of FGPs were obtained.     

THERMOELASTIC PROBLEM OF BONDED ORTHOTROPIC SEMI-INFINITE AND INFINITE STRIPS

The stationary thermoelastic problem for an orthotropic semi-infinite strip bonded to an orthotropic infinite strip is investigated. By using Fourier transforms, the heat conduction problem is reduced to a singular integral equation for the temperature gradient. The associated elasticity problem leads to a system of singular integral equations for strain and stress. Numerical solution of these equations yields temperature, temperature gradient, and stress distributions along the interface, caused by prescribed boundary temperatures.     

Transient Response of a Cracked Piezoelectric Strip Under Thermoelectric Loading

In this study, the theoretical analysis of a transient piezothermoelastic problem is developed for a piezoelectric strip with a parallel crack under static electric loading and thermal shock loading conditions. The crack faces are supposed to be insulated thermally and electrically. By using both the Laplace transform and the Fourier transform, the thermal and electromechanical problems are reduced to a system of singular integral equations, respectively, which are solved numerically. Some numerical results for the temperature change, the stress and electric displacement distributions, and the energy density factor as well as the stress and electric displacement intensity factors in a transient state are shown in figures.     

蓄热式加热炉的热平衡测试与分析

随着蓄热式加热炉的逐步推广应用,近10年迅速成为一项值得推广的节能环保新技术,在不同工业炉上得到快速应用。通过对韶钢蓄热式加热炉的热平衡测试与分析来评价蓄热式加热炉的实际使用效果,以及热平衡测试找出设计、施工和使用中的薄弱环节,为发挥蓄热式加热炉的优势提出建议,为同行建设和使用好蓄热式加热炉提供一些参考。     

Stress response and contact behavior of PEMFC during the assembly and working condition

Mechanical behavior of proton exchange membrane fuel cell (PEMFC) is closely related to its service life. Stress response and contact behavior of PEMFC during the assembly and working condition were investigated. Effects of clamping force, steel bands number and width on the mechanical behavior of PEMFC were discussed. Thermal-mechanical coupling was considered during the PEMFC working for thermal effect caused by chemical reaction. The results show that stress distribution of multi-cells is more uniform after assembly. Stress and contact pressure distributions of single-cell and multi-cells are similar after assembly. During the assembly process, the average contact pressure between the MEA and other parts increases with the increasing of clamping force, steel band width and number. With the steel bandwidth increases, the contact pressure distribution of MEA is more uniform. And the chemical reaction inside the fuel cell is more favorable. Stress concentration is prone to appear on the corners of GDL on the MEA, corners of sealing gasket, and edges of bipolar plate ribs, which may cause seal failure after long-term work. Under working condition, thermal expansion can enhance the sealing performance, but affect stress of bipolar plate and MEA. Those results can be used for design, manufacturing, maintenance and evaluation of PEMFC.